nip10: simplify and fix reply-to-root bugs

This removes EventRefs alltogether and uses the form we use in Damus
Android.

This simplifies our ThreadReply logic and fixes a reply-to-root bug

Reported-by: NotBiebs <justinbieber@stemstr.app>
Changelog-Fixed: Fix thread bug where a quote isn't picked up as a reply
Signed-off-by: William Casarin <jb55@jb55.com>

damus/Util/EventCache.swift

@@ -169,7 +169,7 @@ class EventCache {
         var ev = event
         
         while true {
-            guard let direct_reply = ev.direct_replies(keypair),
+            guard let direct_reply = ev.direct_replies(),
                   let next_ev = lookup(direct_reply), next_ev != ev
             else {
                 break
@@ -183,7 +183,7 @@ class EventCache {
     }
     
     func add_replies(ev: NostrEvent, keypair: Keypair) {
-        if let reply = ev.direct_replies(keypair) {
+        if let reply = ev.direct_replies() {
             replies.add(id: reply, reply_id: ev.id)
         }
     }

damus/Util/ReplyCounter.swift

@@ -39,7 +39,7 @@ class ReplyCounter {
         
         counted.insert(event.id)
         
-        if let reply = event.direct_replies(keypair) {
+        if let reply = event.direct_replies() {
             if event.pubkey == our_pubkey {
                 self.our_replies[reply] = event
             }